Setter plates for solid electrolyte fabrication and methods of using the same to prepare dense solid electrolytes

ABSTRACT

Setter plates are fabricated from Li-stuffed garnet materials having the same, or substantially similar, compositions as a garnet Li-stuffed solid electrolyte. The Li-stuffed garnet setter plates, set forth herein, reduce the evaporation of Li during a sintering treatment step and/or reduce the loss of Li caused by diffusion qui of the sintering electrolyte, Li-stuffed garnet seller plates, set forth herein, maintain compositional control over the solid electrolyte during sintering when, upon heating, lithium is prone to diffuse out of the solid electrolyte.

This application claims priority to, and the benefit of, U.S.Provisional Patent Application Ser. No. 62/148,337, filed Apr. 16, 2015,titled LITHIUM STUFFED GARNET SETTER PLATES FOR SOLID ELECTROLYTEFABRICATION. The entire contents of this application are hereinincorporated by reference in its entirety for all purposes.

BACKGROUND

Cleaner forms of storing energy are in great demand. Examples of cleanenergy storage include rechargeable lithium (Li) ion batteries (i.e.,Li-secondary batteries), in which Li⁺ ions move from a negativeelectrode to a positive electrode during discharge. In numerousapplications (e.g., portable electronics and transportation), it wouldbe advantageous to use a solid state Li ion battery which includes solidstate materials such as solid state electrolytes as opposed to one thatincludes liquid components, (e.g., flammable liquid electrolytes).Using, entirely solid state components improves battery safety andenergy density, the latter of which is due in part to reduced electrodeand electrolyte volume and weight.

Components of a solid state battery include the electrolyte, whichelectrically isolates the positive and negative electrodes, a catholyte,which is intimately mixed with a positive electrode active material toimprove the ionic conductivity therein. A third component, in some Liion batteries, is an anolyte which is laminated to, or in contact with,an anode material (i.e., negative electrode material; e.g., Li-metal).Currently available electrolyte, catholyte, and anolyte materials,however, are not stable within, or otherwise suitable for use with,solid state battery operating voltage ranges or when in contact withcertain cathode or anode active materials such as lithium metal anodes.

Garnet (e.g., Li-stuffed garnet) is a class of oxides that has thepotential to be suitable for use as one or more of a catholyte, anelectrolyte, and an anolyte in a solid state battery. However, garnetmaterials have yet to be prepared with the proper morphology (e.g., thinfilm or nanostructured powder which can be sintered into sufficientlydense films or pellets), with sufficient conductivity or particleconnectivity to function in commercial applications. Certain garnetmaterials and processing techniques are known (e.g., See U.S. Pat. Nos.5,840,436; 8,658,317; 8,092,941; and 7,901,658; or U.S. PatentApplication Publication Nos. 2013/0085055; 2011/0281175; 2014/0093785;2014/0134483; 2015/0099190; 2014/0060723; 2009/0197172; 2010/00119800and 2014/0170504; International Patent Application Publication Nos. WO2010/0051345; 2010/096370 or also Bonderer, et al., Journal of theAmerican Ceramic Society, 2010, 93(11):3624-3631; and Murugan, et al.,Angew Chem, Int. Ed. 2007, 46, 7778-7781), but these materials andtechniques suffer from a variety of deficiencies. The electrolyte filmsmade by these techniques have Insufficient Li⁺ ion conductivity and/orcycle life at high current density and/or low temperatures for use incommercial applications, and these techniques are not compatible withmany battery components.

Accordingly, there is a need for improved methods of making and processnu solid electrolytes such as sintered lithium-stuffed garnetelectrolytes.

SUMMARY

The present disclosure relates generally to the fabrication ofcomponents for lithium rechargeable batteries. Specifically, the presentdisclosure relates to the fabrication of setter plates which includelithium stuffed garnet oxides and to the use of these setter plates tosinter solid electrolytes or solid electrodes for lithium rechargeablebatteries. In some examples, the setter plates described herein areuseful for preparing thin, dense films of lithium-stuffed garnet oxideswhich are highly Li⁺ ion conductive and have a low area-specificresistance (ASR).

The setter plates described herein reduce the chemical potential for Lito diffuse or migrate out of the sintering solid electrolyte (i.e.,herein a “green film” before it is completely sintered) and into thesetter plate or the surrounding atmosphere, thereby preserving thechemical composition of the sintered electrolyte. Furthermore,surprisingly, the thin film Li-stuffed garnet solid electrolytesproduced using Li-stuffed garnet containing setter plates of a same, orsimilar, composition, and as set forth herein, have superior ionicconductivity, also superior mechanical integrity (e.g., lower arealcrack density, lower variation in surface roughness), smaller and moreuniform thicknesses, and also release from the setter platespost-sintering better than when compared to Li-stuffed solidelectrolytes sintered between conventional setter plates which have adifferent chemical composition or Li activity than does the green filmor the solid electrolyte harmed therefrom once sintered.

The disclosure-herein sets forth, inter alia, setter plates useful forfabricating solid electrolytes of a rechargeable battery. The setterplates described herein provide a surface, on top of which, a green filmincluding lithium-stuffed garnets or the chemical precursors thereto maybe sintered. In some examples, the setter plates described hereinprovide surfaces, between which, a green film including lithium-stuffedgarnets or the chemical precursors thereto may be sintered. By sinteringa green film using the setter plates set forth herein, the chemicalcomposition of the sintering film is controlled. The chemicalcomposition of the sintering film is controlled, in part, because thesetter plates described herein maintain the appropriate Li activity orLi chemical potential between the sintering films and the setter platein contact therewith. The chemical composition of the sintering film iscontrolled, in part, because the setter plates described herein maintainthe appropriate Li activity or Li chemical potential between thesintering films and the atmosphere in contact therewith.

Also set forth herein are stacked, repeated units setter plates havinggreen films therebetween which are useful for large scale processing ofsolid electrolytes. In some of these examples, each unit includes atleast two setters and a green film positioned between the setters and incontact with each of the at least two setters. In some examples, severalor more of these units, each which include two setters and a film inbetween the setters, are arranged in arrays. In some examples, thearrays are stacked. In some examples, the units are stacked intocolumns.

These setter plates are in some examples thin monoliths of a Li-stuffedgarnet oxide characterized by the formulaLi_(x)La_(y)Zr_(z)O_(t).qAl₂O₃, wherein 4<x<10, 1<y<4, 1<z<3, 6<t<14,and 0≦q≦1. The value of subscript t is selected such that the garnetoxide characterized by the formula Li_(x)La_(y)Zr_(z)O_(t).qAl₂O₃ ischarge neutral. Any subscript values not specified are limited to thosesubscript values which result in a charge neutral compound description.In some examples, q is 0.1. In some examples, q is 0.2. In someexamples, q is 0.3. In some examples, q is 0.4. In some examples, q is0.5. In some examples, q is 0.6. In some examples, q is 0.7. In someexamples, q is 0.8. In some examples, q is 0.9. In some examples, q is1.0. In some examples, q is 0.21. In some examples, q is 0.22. In someexamples, q is 0.23. In some examples, q is 0.24. In some examples, q is0.25. In some examples, q is 0.26. In some examples, q is 0.27. In someexamples, q is 0.28. In some examples, q is 0.29. In some examples, q is0.91. In some examples, q is 0.92. In some examples, q is 0.93. In someexamples, q is 0.94. In some examples, q is 0.95. In some examples, q is0.96. In some examples, q is 0.97. In some examples, q is 0.98. In someexamples, q is 0.99. In certain examples, these setter plates have asurface defined by a first lateral dimension from about 5 cm to about 20cm and a second lateral dimension from about 5 cm to about 20 cm; and athickness from about 1 mm to about 100 mm. Depending on the dimensionsof a given rechargeable battery for which the setter plate is used tomake a sintered garnet electrolyte, these setter plates can be increasedin size (e.g., surface area increased). For example, depending on thedimensions of a given rechargeable battery for which the setter plate isused to make a sintered garnet electrolyte, the setter side is about 10cm by 7 cm, or also 4 cm by 4 cm, also up to 15 cm by 25 cm, or even upto 96 cm by 96 cm in order to prepay electrolytes having largerdimensions than the particular Examples and embodiments describedherein. A variety of sizes of setter plates may be prepared inaccordance with the features described herein.

Also set forth herein are methods of making setter plates. In someexamples, the method of making a Li-stuffed garnet setter plate includemixing lithium-stuffed garnets and/or the chemical precursors thereto,to form a mixture, in proportions sufficient to produce, upon reaction,a Li-stuffed garnet compound having a composition ofLi_(x)La_(y)Zr_(z)O_(t).qAl₂O₃, wherein 4<x<10, 1<y<4, 1<z<3, 6<t<14,and 0≦q≦1. The subscripts x, y, z, and t, and the coefficient, q, areselected so that the compound is charge neutral. In some examples, themethod further includes calcining the mixture. In certain examples, themethod further includes milling the mixture before calcining themixture. In some examples, the methods include milling the mixture aftercalcining the mixture. In some examples, the methods include mining themixture before and after calcining the mixture. In some examples, themethods include forming (e.g., pressing) the milled precursor materialsinto a pellet or setter plate including the Li-stuffed garnet; placingthe pellet or setter plate onto a substrate; sintering the pellet at atemperature of from 450° C. to 1300° C.; and optionally cooling thepellet in air at 1 atmosphere of pressure and 25° C. In some examples,the sintering is at a temperature of at least 1000° C. In some examples,the sintering is at a temperature of at least 1000° C. and less than1300° C.

In some other examples of methods of making setter plates, the methodsinclude the following steps. In a first step, garnet precursor chemicalsare mixed to form a mixture. In some examples, during this first step,the garnet precursor chemicals are mixed with other oxide or oxideprecursor chemicals to form a mixture. In a second step, the mixture ismilled. In some examples, the mixture is milled to reduce the particlesize and/or increase the surface area of the precursor chemicals. Insome examples, the precursor chemicals are not calcined. In someexamples, the mixture is formed into a form factor suitable for use as asetter plate. In some examples, the form factor is sintered to form asetter plate.

In some other examples, set forth herein are methods of using setterplates. Some of these methods of using a Li-stuffed garnet setter plateinclude fabricating a Li-stuffed garnet solid electrolyte for arechargeable battery include placing unsintered Li-stuffed garnetprecursor materials between two Li-stuffed garnet setter plates; andsintering the unsintered film between the two Li-stuffed garnet setterplates. In some examples, the unsintered Li-stuffed garnet precursormaterials are unsintered films of garnet precursors, binders,dispersants, solvent, polymers, and combinations thereof, also knownherein as green films which may be tape-cast or otherwise provided. Someof these methods of using a Li-stuffed garnet setter plate includefabricating a Li-stuffed garnet solid electrolyte for a rechargeablebattery, placing and unsintered film of Li-stuffed garnet precursormaterials oh top of a Li-stuffed garnet setter plate, and sintering theunsintered film on top of the Li-stuffed garnet setter plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates setter plates and a method of using the setterplates in the preparation of battery materials, in an embodiment.

FIG. 1B illustrates a plan view and a cross-sectional view of aLi-stuffed garnet setter plate of the present disclosure taken throughline A-A′ in FIG. 1B, in an embodiment.

FIG. 2 illustrates a method of fabrication of Li-stuffed garnet setterplates, in an embodiment.

FIG. 3A is a cross-sectional scanning electron micrograph (SEM) of aLi-stuffed garnet setter plate of the present disclosure fabricatedaccording to the method illustrated in FIG. 2 in an embodiment.

FIG. 3B is a cross-sectional SEM of a Li-stuffed garnet setter plate ofthe present disclosure that was thermally cycled (i.e., seasoned) toincrease its grain size and reduce its tendency to adhere to sinteringgreen films, in an embodiment.

FIG. 4 illustrates four surface roughness measurements from a Li-stuffedgarnet setter plate fabricated according to the method shown in FIG. 2,in an embodiment.

FIGS. 5A-5D illustrate X-ray diffraction (XRD) spectra for sinteredLi-stuffed garnet electrolytes which were sintered with either polishedsmall grain setter plates, unpolished small grain setter plates,polished large grain setter plates, or unpolished large grain setterplates, in certain embodiments. As noted in the method illustrated inFIG. 2, setter plates are Initially polished following theirpreparation. Unpolished herein refers to a setter that has beenthermally cycled (e.g., heated, i.e., seasoned) but not subsequentlypolished after the thermal cycle. Polished herein refers to a setterthat has been thermally cycled and subsequently polished.

FIG. 6 illustrates a method of using Li-stuffed garnet setter to sintera Li-stuffed garnet solid electrolyte, in an embodiment.

FIG. 7 illustrates an Arrhenius plot (log(σ) v. 1000/T in Kelvin) ofelectrical impedance spectroscopy (EIS) results for solid stateLi-stuffed electrolytes films fabricated according to the methodillustrated in FIG. 6 and sintered between two Li-stuffed garnetcontaining setter plates and in which lithium metal was deposited ontothe sintered electrolyte and then tested for ionic conductivity at 20°C., 50° C., 60° C., and 80° C. in a symmetric Li|Garnet|Li cell.

FIG. 8 shows DC Testing results for a Li-stuffed garnet electrolytefabricated according to the method illustrated in FIG. 6 and sinteredbetween two Li-stuffed garnet containing setter plates of the presentdisclosure and in which the electrolytes were tested in a symmetricLi|Garnet|Li cell.

FIG. 9 shows an example of an EIS (AC Impedance) testing at 60° C. for aLi-stuffed garnet electrolyte prepared using Li-stuffed setter plates ofthe present disclosure and in which the electrolytes were tested in asymmetric Li|Garnet|Li cell.

FIG. 10 shows XRD spectra for three lithium-stuffed garnet filmsfabricated according to the method illustrated in FIG. 6 and sinteredbetween either two ZrO₂ setter plates (top, A), two Al₂O₃ setter plates(middle, B), or two lithium-stuffed garnet setter plates (bottom, C).

The figures depict various embodiments of the present disclosure forpurposes of illustration only. One skilled in the art will readilyrecognize from this following discussion that alternative embodiments ofthe structures and methods illustrated herein may be employed withoutdeparting from the principles described herein.

DETAILED DESCRIPTION Definitions

U.S. Patent Application Publication U.S. 2015/0099190, which publishedApr. 9, 2015 and was filed Oct. 7, 2014 as Ser. No. 14/509,029, isincorporated by reference herein in its entirety. This applicationdescribes Li-stuffed garnet solid-state electrolytes used in solid-statelithium rechargeable batteries. These Li-stuffed garnets generallyhaving a composition according to Li_(A)La_(B)M′_(C)M″_(D)Zr_(E)O_(F),Li_(A)La_(B)M′_(C)M″_(D)Ta_(E)O_(F), orLi_(A)La_(B)M′_(C)M″_(D)Nb_(E)O_(F), wherein 4<A<8.5, 1,5<B<4, 0≦C≦2,0≦D≦2; 0≦E<2, 10<F<13, and M′ and M″ are each, independently in eachinstance selected from Al, Mo, W, Nb, Sb, Ca, Ba, Sr, Ce, Hf, Rb, or Ta,or Li_(a)La_(b)Zr_(c)Al_(d)Me″_(e)O_(f), wherein 5<a<8.5; 2<b<4;0<c≦2.5; 0≦d<2; 0≦e<2, and 10<f<13 and Me″ is a metal selected from Nb,Ta, V, W, Mo, or Sb and as otherwise described in U.S. PatentApplication Publication No. U.S. 2015/0099190. As used, herein,lithium-stuffed garnets, and garnets, generally, include, but are notlimited to, Li_(7.0)La₃(Zr_(t1)+Nb_(t2)+Ta_(t3))O₁₂+0.35Al₂O₃; wherein(subscripts t1+t2+t3=subscript 2) so that the La(Zr/Nb/Ta) ratio is 3.2.Also, garnets used herein includes, hut are not limited toLi_(x)La₃Zr₂O₁₂+yAl₂O₃, wherein x ranges from 5.5 to 9; and y rangesfrom 0 to 1. In these examples, x and y are selected so that the garnetis charge neutral. In some examples x is 7 and y is 1.0. In someexamples, x is 5 and y is 1.0. In some examples, x is 6 and y is 1.0. Insome examples, x is 8 and y is 1.0. In some examples, x is 9 and y is1.0. In some examples x is 7 and y is 0.35. In some examples, x is 5 andy is 0.35. In some examples, x is 6 and y is 0.35. In some examples, xis 8 and y is 0.35. In some examples, x is 9 and y is 0.35. In someexamples x is 7 and y is 0.7. In some examples, x is 5 and y is 0.7. Insome examples, x is 6 and y is 0.7. In some examples, x is 8 and y is0.7. In some examples, x is 9 and y is 0.7. In some examples x is 7 andy is 0.75. In some examples, x is 5 and y is 0.75. In some examples, xis 6 and y is 0.75. In some examples, x is 8 and y is 0.75. In someexamples, x is 9 and y is 0.75. In some examples x is 7 and y is 0.8. Insome examples, x is 5 and y is 0.8. In some examples, x is 6 and y is0.8. In some examples, x is 8 and y is 0.8. In some examples, x is 9 andy is 0.8. In some examples x is 7 and y is 0.5. In some examples, x is 5and y is 0.5. In some examples, x is 6 and y is 0.5. In some examples, xis 8 and y is 0.5. In some examples, x is 9 and y is 0.5. In someexamples x is 7 and y is 0.4. In some examples, x is 5 and y is 0.4. Insome examples, x is 6 and y is 0.4. In some examples, x is 8 and y is0.4. In some examples, x is 9 and y is 0.4. In some examples x is 7 andy is 0.3. In some examples, x is 5 and y is 0.3. In some examples, x is6 and y is 0.3. In some examples, x is 8 and y is 0.3. In some examples,x is 9 and y is 0.3. In some examples x is 7 and y is 0.22. In someexamples, x is 5 and y is 0.22. In some examples, x is 6 and y is 0.22.In some examples, x is 8 and y is 0.22. In some examples, x is 9 and yis 0.22. Also, garnets as used herein include, but are not limited to,Li_(x)La₃Zr₂O₁₂+yAl₂O₃. In one embodiment, the Li-stuffed garnet used tofabricate setter plates of the present disclosure has a composition ofLi₇Li₃O₁₂. In another embodiment, the Li-stuffed garnet used tofabricate Setter plates of the present disclosure has a composition ofLi₇Li₃Zr₂O₁₂.Al₂O₃. In yet another embodiment, the Li-stuffed garnetused to fabricate setter plates of the present disclosure has acomposition of Li₇Li₃Zr₂O₁₂.0.22Al₂O₃. In yet another embodiment, theLi-stuffed garnet used to fabricate setter plates of the presentdisclosure has a composition of Li₇Li₃Zr₂O₁₂.0.35Al₂O₃. In certain otherembodiments, the Li-stuffed garnet used to fabricate setter plates ofthe present disclosure has a composition of Li₇Li₃Zr₂O₁₂.0.5Al₂O₃. Inanother embodiment, the Li-stuffed garnet used to fabricate setterplates of the present disclosure has a composition ofLi₇Li₃Zr₂O_(12.)0.75Al₂O₃.

As used herein, garnet does not include YAG-garnets (i.e., yttriumaluminum garnets, or, e.g., Y₃Al₅O₁₂). As used herein, garnet does notinclude silicate-based garnets such as pyrope, almandine, spessartine,grossular, hessonite, or cinnamon-stone, tsavorite, uvarovite andandradite and the solid solutions pyrope-almandine-spessarite anduvarovite-grossular-andradite. Garnets herein do not includenesosilicates having the general formula X₃Y₂(SiO₄)₃ wherein X is Ca,Mg, Fe, and, or, Mn; and Y is Al, Fe, and, or, Cr.

As used herein, the phrases “garnet precursor chemicals,” “chemicalprecursor to a garnet-type electrolyte,” “precursors to garnet” and“garnet precursor materials” refer to chemicals which react to form alithium stuffed garnet material described herein. These chemicalprecursors include, but are not limited to lithium hydroxide (e.g.,LiOH), lithium oxide (e.g., Li₂O), lithium carbonate (e.g., LiCO₃),zirconium oxide (e.g., ZrO₂), lanthanum oxide (e.g., La₂O₃), lanthanumhydroxide (e.g., La(OH)₃), aluminum oxide (e.g., Al₂O₃), aluminumhydroxide (e.g., Al(OH)₃), aluminum (e.g., Al), aluminum nitrate (e.g.,Al(NO₃)₃), aluminum nitrate nonahydrate, niobium oxide (e.g., Nb₂O₅),and tantalum oxide (e.g., Ta₂O₅). Other precursors to garnet materials,known in the relevant field to which the instant disclosure relates, maybe suitable for use with the methods set forth herein.

As used herein the phrase “garnet-type electrolyte,” refers to anelectrolyte that includes a lithium stuffed garnet material describedherein as the Li⁺ ion conductor. The advantages of Li-stuffed garnetsolid-state electrolytes are many, including as a substitution forliquid, flammable electrolytes commonly used in lithium rechargeablebatteries.

As used herein, the phrase “d₅₀ diameter” refers to the median size, ina distribution of sizes, measured by microscopy techniques or otherparticle size analysis techniques, such as, but not limited to, scanningelectron microscopy or dynamic light scattering. D₅₀ describes acharacteristic dimension of particles at which 50% of the particles aresmaller than the recited size.

As used herein, the phrase “grain size” refers the characteristicdimension, or maximum dimension (e.g., diameter of a spherically-shapedgrain), defining a region that has a homogeneous composition,crystalline structure, and crystal orientation. Grains can be observedby high resolution TEM or electron back-scatter diffraction (EBSD).

The term “unpolished” in the context of a setter plate refers to asetter plate that has been thermally cycled (e.g., heated or seasoned)but not subsequently polished.

The term “polished” in the contest of a setter plate refers to a setterplate that has been thermally cycled (e.g., heated or seasoned) andsubsequently polished.

As used herein, “thermally cycling” in the context of a setter platerefers to heating a setter plate without sintering a green filmthereupon.

As used herein, the phrase “green film” refers to an unsintered filmincluding at least one member selected from garnet materials, precursorsto garnet materials, binder, solvent, carbon, dispersant, orcombinations thereof.

As used herein, “flatness” of a surface refers to the greatest normaldistance between the lowest point on a surface and a plane containingthe three highest points on the surface, or alternately, the greatestnormal distance between the highest point on a surface and a planecontaining the three lowest points on the surface. It may be measuredwith an AFM, a high precision optical microscope, or laserinterferometry height mapping of a surface.

As used herein, “porosity” of a body is the fractional volume that isnot occupied by material. It may be measured by mercury porosimetry orby cross-sectioning the body and optically determining the 2D fractionalarea of porosity of the cross-sectioned surface.

The preparation of the Li-stuffed garnet solid state electrolytes, at ahigh level, involves preparing a mixture of precursor materials,calcined garnet materials, or combinations thereof and binders. In someexamples, the preparation further includes pressing, providing orforming the mixture into a desired form factor (such as a plate, disk,film, or pellet) or cast (e.g., tape cast, slot-die, screen print,slip-cast, gel-cast, or doctor-bladed) as a film. In some examples, thepreparation further includes sintering the mixture or film under thepressure applied to the sintering electrolyte on account of the weightof the setter placed in contact with the sintering mixture of film.Certain preparation methods for solid state electrolytes are alsodescribed in U.S. Patent Application Publication No. U.S. 2015/0099190,which published Apr. 9, 2015 and was filed Oct. 7, 2014, which isincorporated by reference herein in its entirety.

Overview

Ion (e.g., Li⁺) mobility is typically lower in solid state electrolytescompared to ion mobility in conventionally used, flammable, liquidelectrolytes. To compensate for this lower ion mobility, the solidelectrolyte dimensions, such as the thickness of a film, are reduced(from approximately 200 microns or 100 microns to approximately 50microns or 10 microns) so that a significantly reduced ion migrationdistance through the solid state electrolyte (compared to theconventional liquid electrolyte) compensates for the lower mobility. Theresult is a solid state electrolyte that provides energy delivery rates(i.e., power) comparable to, or superior to, energy delivery rates ofsecondary batteries using flammable, liquid electrolytes.

However, challenges remain in the fabrication of a solid stateelectrolyte thinner than approximately 100 microns and with sufficientmechanical integrity to operate reliably within a solid-state battery.For example, cracks, voids, and other in homogeneities can act asnucleation sites for lithium ions. As the lithium ions nucleate at thesesites, metallic lithium can continue to accrete at these sites duringdischarge of the battery and can lead to shorting of the battery oncelithium dendrites electrically connect the anode to the cathode or viceversa. In other situations, inhomogeneities, cracks, and/or surfaceroughness can increase resistance at interfaces between the solid stateelectrolyte and the corresponding positive and negative electrodes. Thishas the effect of reducing battery efficiency and power. Furthermore, asmentioned above, maintaining stoichiometry of a solid state electrolyteis an important factor in proper functioning of the battery in termspower and energy delivery efficiency.

Embodiments of the present disclosure use Li-stuffed garnet setterplates or setter plates which include a Li-stuffed garnet oxide to applypressure to similarly, substantially similarly, or identically composedLi-stuffed solid electrolytes films, wherein the pressure applied isrelated to the weight of the setter plate. Additional external pressuresare typically not applied to the setter plate; rather the setter plateis designed so that the weight of the plate is sufficient to press ontoa sintering film and form a smooth surface but not to crack thesintering film as it is sintering or after it is sintered. As is shownin FIG. 1, Li-stuffed garnet setter plates 100 are used to applypressure to a dried slurry (referred to herein and in U.S. PatentApplication Publication No. 2015-0200420 as a “green film”) of precursormaterials and binders 104 during sintering. In some examples, the driedslurry is referred to as a green tape. In some examples, a green film isa dried slurry of unsintered materials. Solid state electrolytes havebeen fabricated herein using “setter plates” that apply pressure tosolid electrolyte precursor materials prior to and during sintering.These plates are normally flat and do not generally react with thesintered material. Conventional inert setter plates can be metallic(e.g., platinum) or ceramic (e.g.; zirconia (ZrO₂) or alumina (Al₂O₃))and, optionally, can be porous to provide for the diffusion of gases andvapors therethrough during sintering. However, several problems areassociated with conventional setter plates, such as adherence of theconventional setter plates to the sintering thin film or destruction ofthe Li-stuffed garnet chemical composition in the sintering thin film.

In some examples described herein, other setter plates may be used, forexample in combination with the lithium stuffed garnet setter platesdescribed herein, so long as that other setter plate has a high meltingpoint, a high lithium activity, and stability in a reducing environment.Some examples of these other materials include a member selected fromLi₂ZrO₃, xLi₂O-(1-x)SiO₂ (where x=0.01-099), aLi₂O-bB₂O₃-cSiO₂ (wherea+b+c=1), LiLaO₂, LiAlO₂, Li₂O, Li₃PO₄, a Li-stuffed garnet, orcombinations thereof. In some embodiments, the other setter platescomprise Li₂ZrO₃. In some embodiments, the other setter plates compriseLi₂SiO₃. In some embodiments, the other setter plates comprise LiLaO₂.In some embodiments, the other setter plates comprise LiAlO₂. In someembodiments, the other setter plates comprise Li₂O. In some embodiments,the other setter plates comprise Li₃PO₄. In some embodiments, the othersetter plates comprise a Li-stuffed garnet. In some embodiments, theother setter plates comprise at least two, three, four or more ofLi₂ZrO₃, Li₂SiO₃, LiLaO₂, LiAlO₂, Li₂O, Li₃PO₄, and a Li-stuffed garnet.Additionally, these other setter plates should not induce a chemicalpotential in the sintering film which results in Li diffusion out of thesintering film, for example, into the setter plate.

While some setter plates could be fabricated from other unrelatedgarnet-type materials (i.e., having a composition according toX₃Y₂(SiO₄)₃ where X is a divalent cation (e.g., Ca²⁺, Mg²⁺, Fe²⁺, Mn²⁺)and Y is a trivalent cation (e.g., Al³⁺, Fe³⁺, Cr³⁺)), these otherunrelated garnet-type setter plate compositions, even thoughstructurally garnet, are not suitable for fabrication of lithium-stuffedgarnet solid electrolytes for lithium secondary batteries. Conventionaland/or commercially available setter plates, when in contact with asintering Li electrolyte, result in a chemical potential that drives Liloss (e.g., Li diffusion out of the electrolyte) during the sinteringprocess and destruction of the chemical composition of the Lielectrolyte (e.g., destruction of, or change in, the Li-stuffed garnetcomposition). Even assuming that some of these other setter plates wereable to fee used to sinter Li-stuffed garnet solid electrolytes havingsurfaces sufficiently smooth and with sufficient mechanical integrity(i.e., few or no cracks, pores, or inhomogeneities that act as sites formechanical failure of metallic lithium nucleation), deficiencies remain.For example, conventional setter plates, whether ZrO₂, Al₂O₃, orplatinum alloy with lithium, permit the diffusion of lithium from theprecursor materials into the setter plates. Thus, at sinteringtemperatures, the Li-stuffed solid electrolyte changes composition aslithium diffuses into the setter plates. This, in turn, reduces theperformance of the solid electrolyte that is produced by this sinteringprocess.

In contrast, embodiments of the present disclosure fabricate setterplates out of garnet materials having the same or substantially similarcomposition as the Li-stuffed garnet solid electrolyte. In addition toproviding a surface by which to apply pressure to the solid stateelectrode precursor mixture, setter plates of the present disclosure donot affect the composition of the Li-stuffed garnet solid electrolyteitself. This has the benefit of maintaining compositional control of thesolid electrolyte itself during sintering when, upon heating, lithium isprone to diffusing out of the solid electrolyte. Furthermore,surprisingly, the Li-stuffed solid electrolyte produced by using setterplates of a same, or substantially similar, composition has superiormechanical integrity (e.g., lower areal crack density, less variation insurface roughness) compared to Li-stuffed solid electrolyte sinteredbetween conventional setter plates having different composition from thesolid electrolyte.

Setters

In some examples, the instant disclosure provides a setter platesuitable for use for fabricating solid electrolytes of a rechargeablebattery, wherein the setter plate includes a Li-stuffed garnet compoundcharacterized by the formula Li_(x)La_(y)Zr_(z)O_(t).qAl₂O₃, wherein4<x<10, 1<y<4, 1<z<3, 6<t<14, and 0≦q≦1. In some examples, the setterplate has a surface defined by a first lateral dimension from 2 cm to 30cm and a second lateral dimension from 2 cm to 30 cm; and a thicknessfrom 0.1 mm to 100 mm.

In some examples, the surface is defined by a first lateral dimensionfrom 5 cm to 20 cm and a second lateral dimension from 5 cm to 20 cm.

In some examples, the thickness is from 1 mm to 100 mm. In otherexamples, the thickness is from 0.1 mm to 10 mm. In still otherexamples, the thickness is from 0.5 mm to 5 mm. In some other examples,the thickness is from 1 mm to 1.5 mm.

In some examples, the Li-stuffed garnet compound comprises grains from 1microns in diameter to 400 microns in diameter. In some examples, theLi-stuffed garnet compound comprises grains having a grain size from 2microns to 10 microns. In other examples, the Li-stuffed garnet compoundcomprises grains having a grain size from 100 microns to 400 microns.

In some examples of the setter plates set forth herein, the surface ofthe setter plate has a surface roughness from 1.0 μm R. to 4 μm Ra,wherein Ra is an arithmetic average of absolute values of sampledsurface roughness amplitudes. In some examples, the surface has asurface roughness from 0.5 μm Rt to 30 μm Rt, wherein Rt is the maximumpeak height of sampled surface roughness amplitudes. In some examples,the surface roughness is from 1.6 μm Ra to 2.2 μm Ra. In other examples,the surface roughness is from 3.2 μm Ra to 3.7 μm Ra. In still otherexamples, the surface roughness is from 1 μm Rt to 28 μm Rt. In someother examples, the surface roughness is from 10 μm Rt to 30 μm Rt. Incertain examples, the surface roughness is from 15 μm Rt to 30 μm Rt. Insome examples, the crystallite size in the grains is about 200 nm to 1μm. In some examples, the crystallite size in the grains is about 100 nmto 5 μm.

In some examples, q is 0.35 or 1. In some examples, the formula,characterizing the setter plate is Li7La₃Zr₂O₁₂.qAl₂O₃, wherein q is 0,0.3, 0.35, 0.5, 0.75, or 1.0.

In some examples, set forth herein is a setter plate suitable for usefor fabricating solid electrolytes of a rechargeable battery, whereinthe setter plate includes an oxide material with lithium concentrationgreater than 0.02 mol/cm³ and a melting point above 1100° C. In someexamples, the surface of the setter plate is defined by a first lateraldimension from 3 cm to 30 cm and a second lateral dimension from 3 cm to30 cm; and a thickness from 0.1 mm to 100 mm.

In some examples, the setter plate includes an oxide material selectedfrom LiLaO₂.

In some examples, the setter plate includes an oxide material selectedfrom Al₂O₃.

In some examples, the setter plate includes an oxide material selectedfrom ZrO₂.

In some examples, the setter plate Includes an oxide material selectedfrom La₂O₃.

In some examples, the setter plate includes an oxide material selectedfrom LiAlO₂.

In some examples, the setter plate includes an oxide material selectedfrom Li₂O.

In some examples, the setter plate includes an oxide material selectedfrom Li₃PO₄.

In some examples, the setter plate includes an oxide material selectedfrom LiLaO₂, LiAlO₂, Li₂O, Li₃PO₄, or a Li-stuffed garnet compoundcharacterized by the formula Li_(x)La_(y)—Zr_(z)Ot.qAl₂O₃, wherein4<x<10, 1<y<4, 1<z<3, 6<t<14, 0≦q≦1, or combinations thereof.

Method of Making Setters

FIG. 1B illustrates a plan view and a cross-sectional view of aLi-stuffed garnet setter plate of the present disclosure taken throughline A-A′ in FIG. 1A. The plan view 120 illustrates that a Li-stuffedgarnet setter plate of the present disclosure is up to 10 cm per side inone embodiment, although it will be appreciated that other embodimentscan have lateral dimensions greater or smaller than 10 cm. In someembodiments, a lateral dimension is as low as 5 cm and as high as 20 cm.In some other embodiments, a lateral dimension is as low as 1 cm and ashigh as 96 cm. Also, generally the setter plates of the presentdisclosure are square or rectangular, but other embodiments includesetter plates that are any regular or irregular polygon, or even, havecircular or ellipsoidal cross-sections. The cross-sectional view 130illustrates a Li-stuffed garnet setter plate of the present disclosureup to 2 mm thick, in an embodiment. Other embodiments are betweenapproximately 1 mm and 1.5 mm thick. Still other embodiments are asthick as 100 mm. This thickness is a benefit of Li-stuffed garnet setterplates of the present disclosure, which maintain mechanical integrityeven in these relatively thin configurations. However, the setter platescannot be too thick (e.g., areal density greater than 1.7 g/cm²) or theweight of the setter plate may crack or stick to the sintered film thatis positioned between the setter plates. It is therefore advantageous tosize the setter plates. In some examples, such that the weight of thesetter and its size result in an areal density of 1.7 g.cm² or less.

FIG. 2 illustrates one embodiment of a method 200 for fabricatingLi-stuffed garnet setter plates. As shown in FIG. 2, the method 200 can,for convenience of explanation only, be depicted in two meta-steps: rawmaterial preparation 204; and setter plate fabrication 260. The method200 is described below in more detail.

Within raw material preparation 204 meta-step, precursor materials LiOH,Al(No₃)₃.9H₂O, ZrO₂, and La₂O are gathered 208 in quantitiescorresponding to molar amounts of the final Li-stuffed garnet setterplate final composition (Li_(A)La_(B)M′_(c)M″_(D)Zr_(E)O_(F),Li_(A)La_(B)M′_(C)M″_(D)Ta_(E)O_(F), orLi_(A)La_(B)M′_(C)M″_(D)Nb_(E)O_(F), wherein 4<A<5, 1.5<B<4, 0≦C≦2,0≦D≦2; 0≦E<2, 10<F<13, e.g., Li₇La₃Zr₂O₁₂), as described above and asalso described in various experimental examples of U.S. PatentApplication Publication No. U.S. 2015/0099190, which published Apr. 9,2015. In one embodiment precursor materials are combined in proportionsthat, when reacted, produce a composition of Li₇Li₃Zr₂O₁₂ orLi₇Li₃Zr₂O₁₂(0.35-1.0)Al₂O₃. The precursor materials are dried 212 at120° C. for at least 45 minutes. The dried precursor materials mixed andare optionally in some embodiments milled 216 in a ball mill between 6and 8 hours using, in some examples, 0.3 mm yttria-stabilized zirconiumoxide grinding media beads. The result is a particle size distributionof precursor materials with a d₅₀ of approximately 100 nm. In someexamples, the result is a particle size distribution of precursormaterials with a d₅₀ of approximately 100 nm to 600 nm. The precursormaterials are optionally crushed using a Retzsch mill, and sieved 220using a 40 mesh sieve for 5 minutes. The precursor materials are thenplaced in an alumina crucible, covered, and calcined 224 at about 900°C. (or at a temperature ranging from 400° C. to 1200° C.) forapproximately 6 hours (or for about 2, 4, 6, or 8 hours). The calcinedproduct is then crushed 228 with, for example, a mortar and pestlealthough other grinding and milling mechanisms may be used. The calcinedand crushed precursor materials are then attrition milled 232 bysuspending approximately 62. weight % solids and 10 weight % dispersant,with a suspension media such as isopropyl alcohol making up the balanceof the weight (i.e., approximately 27.5 weight %). In some examples,step 232 includes about 60 g of garnet, about 30 g of solvent, and about10 g of dispersant. In some examples, the solvent is isopropanol andbutanol.

Examples of dispersants, used to facilitate suspension of the calcinedand crushed precursor materials in the isopropyl alcohol include, butare not limited to, phosphate esters, RHODOLINE™ 4160, RHODOLINE™ 4188,Phoschem R6, Phoschem PD, phospholan-131™, esters such, as fish oil,BYK™ 22124, surfactants, fluorosurfactants, polyvinylpyridine (PVP),polyvinyl butadiene (PVB), TRITON™, phospholan-131™, BYK™ 22124, BYK™22416, Hypermer KD1™, polyalkylene amine such as Hypermer KD2, acrylicpolymers such as Hypermer KD6™, Hypermer KD7™, and others, such asDispersbyk-118, BYK™ 22146, Hypermer KD7™. While isopropyl alcohol isused in this example, other solvents may also be used including toluene,ethanol, combinations thereof (i.e., toluene:ethanol::4:1) and others.The attrition milling may be performed for approximately eight hourswith an inert zirconia grinding media to produce a d₅₀ particle sizedistribution from approximately 100 nm to approximately 1μm (e.g., fromapproximately 300 nm to approximately 400 nm).

Meta-step 260 begins with the slurry produced by meta-step 232 as aninput. The slurry is optionally centrifuged 264 at 2000 rpm for 1-12hours. Step 264 is optional and may or may not be used. If, however, theslurry is centrifuged 264, the supernatant is drained and the percentageof solids in the remaining slurry is determined 268. If the slurry isnot centrifuged, the solid loading is determined and adjustedappropriately. In some examples the percentage of solids in the slurryis between approximately 40 weight %, 50 weight % 60 weight % or 70weight % or any weight % that falls between any two of these values. Insome examples, the slurry is adjusted or prepared so that the slurryincludes, in relative amounts respectively, approximately 60 g ofgarnet, approximately 100 g of solvent, approximately 4 g of binder(PVB) and approximately 1 g of plasticizer (e.g., dibutyl phthalate,benzyl dutyl phthalate, and the like).

The slurry is then mixed 272 with a 4 weight % solution of polyvinylbutyral binder in toluene in a weight ratio of 1:1. This mixture is thendried, mechanically crushed (for example, using a mortar and pestle),and sieved 276, for example, using an 80 mesh sieve. Resulting from 276is a slurry having approximately 100 g of garnet, 4 g of binder, and 1 gof plasticizer.

The combined Li-stuffed garnet powder, solvent, binder, and plasticizerare then mixed and milled using techniques described above. As noted inFIG. 2, the approximate composition of combination is in some examples:about 50 wt % powder, 47.5 wt % solvent, 2 wt % binder and 0.5 wt %plasticizer. Binders and solvents are described herein, above and below.The combined components are then mixed and/or optionally milled forapproximately 8 hours (e.g., by band stirring although the componentscan be combined using appropriate mixer or blender). The mixedcomponents are placed on a hot plate or oven to remove the solvents asper step 276 in FIG. 2. Other methods to remove solvents, such asROTO-VAP™ or spray drying could also be used.

The powder produced after drying, crushing and sieving 276 is pressed280 into a setter plate format using a mechanical press andcorresponding die. For example, forming, a setter plate Into a format ofa square, approximately 2.5 cm on a side includes applying 2000 lbs offorce to the powder. In other examples, the method includes forming asetter plate into a format of a square approximately 10 cm on a sideincludes applying 2000 lbs of force to the powder.

The pressed plate is then placed between, or on top of, commerciallyavailable (e.g., platinum) setter plates (or alternatively on a singlesubstrate) and sintered 284 in a furnace at from approximately 500° C.to approximately 1300° C. (and preferably from 1075° C. to approximately1150° C.) in an argon atmosphere, for approximately three hours toapproximately six hours. In some examples, the setter plate is removedfrom the furnace and placed at room temperature to air quench. In someother examples, the setter plate is left in the oven to cool over manyhours for at least 2, 3, 4, 6, 12, 15, 18. 24, 30 or 36 hours). The ramprate of the furnace is from about 1° C./min to about 10° C./min. Onceremoved from the furnace, the Li-stuffed garnet setter plate is polished288 sequentially with 30 micron, 15 micron, 9 micron, and 5 micronalumina polishing powders. In some examples, the setter is polishedusing 30 microns alumina polishing powder.

In some examples, the setter plates are then subsequently thermallycycled (e.g., seasoned) to reduce the tendency of the setter plate tostick to a given sintered film. As used herein, thermally cyclingincludes heating the setter plates/without sintering a green filmthereupon. This thermal cycling is associated with a grain growth in thesetter plate. In between thermal cycling, the setter plate is eitherpolished or is not polished. If the setter plate is polished following athermal cycling, the setter plate is referred herein as a polishedsetter plate. If the setter plate is not polished following a thermalcycling, the setter plate is referred herein as an unpolished setterplate.

In some examples, set forth herein is a method of making a Li-stuffedgarnet setter plate which includes mixing precursor materials, to form amixture, in proportions sufficient to produce, upon reaction, aLi-stuffed garnet compound having a composition ofLi_(x)La_(y)—Zr_(z)O_(t).qAl₂O₃, wherein 4<x<10, 1<y<4, 1<z<3, 6<t<14,0≦q≦1; optionally calcining the mixture to form garnet powder; millingthe mixture or the garnet powder, forming a pellet of the Li-stuffedgarnet setter plate; placing the pellet onto a substrate; sintering thepellet at a temperature of from 450° C. to 1300° C. and optionallycooling the pellet in air at 1 atmosphere of pressure and 25° C.

In some examples, the methods herein include forming a pellet comprisespressing the mixture or the garnet powder into a pellet of theLi-stuffed garnet setter plate.

In some examples, the methods herein include polishing the garnet setterplate.

In some examples, the methods herein include milling the mixed precursormaterials including incorporating a binder or polymer selected fromnitriles, nitrite butadiene rubber, carboxymethyl cellulose (CMC),styrene butadiene rubber (SBR), PVDF-HFP, PAN, aqueous-compatiblepolymers, atactic polypropylene (aPP), silicone, polyisobutylene (PIB),ethylene propylene rubber (EPR), PMX-200 PDMS(polydimethylsiloxane/polysiloxane, i.e., PDMS or silicone),polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polyvinylchloride (PVC), poly vinylbutyral (PVB), or poly(vinylidene)fluoride-hexafluoropropylene PVDF-HFP.

In some examples, the binder is PVB or Duramax B-1000 or Duramax B-1022or polyethylineimine.

In some examples, the methods herein include using the pellet in aseasoning sintering cycle.

In some examples, the substrate is a metal. In some examples, thesubstrate is metallic platinum or nickel.

In some of the methods herein, the proportions of the precursormaterials are mixed to produce, upon reaction, a Li-stuffed garnetcompound have the composition of Li_(x)Li₃Zr₂O₁₂.qAl₂O₃, wherein q is 0,0.35, 0.5, 0.75, or 1 and x is between 5.0-7.7.

Method of Making Sintered Electrolyte Films

In some examples, an unsintered thin film is prepared or cast so that itcan be placed between setter plates in a subsequent sintering procedure.This process includes a slurry preparation step in which a combinationof milled Li-stuffed garnet powder that is a product of the meta-step204 is combined with one or more solvents, a binder, and a plasticizer(such as dibutyl phthalate).

In some examples, the slurry includes a solvent selected fromisopropanol, water, butanol, tetrahydrofuran (THF), with a binder (e.g.,PVB), and/or a plasticizer. In some examples, the solvent includes about10-30% w/w isopropanol, 1-10% w/w water, 1-10% w/w butanol, and 10-30 %w/w tetrahydrofuran (THF) [e.g. 100 grams garnet, 12 grams binder, 12grams DBF, 20-30 grams solvent]. In some examples, the solvent includesabout 20-30% w/w isopropanol, 3-6% w/w water, 3-6% w/w butanol, and20-30 % w/w tetrahydrofuran (THF). In some examples, the binder is 5%w/w. In some examples, the plasticizer is 5% w/w. In these examples, thegarnet or calcined precursor materials represent the remaining % w/w(e.g., 40, 50, or 60% w/w). In some examples, a dispersant is usedduring the milling process. In some examples, the dispersant is aphosphate ester. In some examples, the plasticizer is dibutyl phthalateor benzyl butyl phthalate. In some examples, the solvent is butanol andTHF. In some examples, the solvent is butanol, water and THF. In someexamples, the solvent is butanol, water, toluene, and THF. In someexamples, the solvent is butanol and toluene. In some examples, thesolvent is butanol, water and THF.

Examples of solvents include toluene, ethanol, diacetone alcohol, andcombinations thereof. Other examples of solvents include combinations ofisopropanol, butanol, and toluene. Other examples of solvents includemethanol, ethanol, isopropanol, butanol, pentanol, hexanol, toluene,xylene, tetrahydrofuran, toluene methanol, acetone,N-methyl-2-pyrrolidone (NMP) diacetone alcohol, ethyl acetate,acetonitrile, hexane, nonage, dodecane, methyl ethyl ketone (MEK), andcombinations thereof.

Examples of binders, used to facilitate the adhesion between theLi-stuffed garnet particles, include, but are not limited to,polypropylene (PP), polyvinyl butyral (PVB), poly ethyl methacrylate(PMMA); polyvinyl pyrrolidone (PVP), atactic polypropylene (aPP),isotactive polypropylene ethylene propylene rubber (EPR), ethylenepentene copolymer (EPC), polyisobutylene (PIB), styrene butadiene rubber(SBR), polyolefins, polyethylene-copoly-1-octene (PE-co-PO);PE-co-poly(methylene cyclopentane) (PE-co-PMCP); stereo blockpolypropylenes, polypropylene polymethylpentene copolymer, polypropylene carbonate, methyl methacrylate, ethyl methacrylate, andsilicone. Other binders include binder is selected polypropylene (PP),atactic polypropylene (aPP), isotactic polypropylene (iPP), ethylenepropylene rubber (EPR), ethylene pentene copolymer (EPC),polyisobutylene (PIB), sytrene butadiene (SBR), polyolefins,polyethylene-co-poly-1-octene (PE-co-PO) PE-co-poly(methylenecyclopentene) (PE-co-PMCP), stereoblock polypropylenes, polypropylenepolymethyl pentene, polyethylene oxide (PEO), PEO block copolymers,silicone, and combinations thereof.

In order to make unsintered tape-cast films (i.e., green films), whichcan be placed between setter plates for sintering, tire following stepsmay be employed. The garnet precursors are combined with solvent andhinder In amounts snob that after sintering, the ratio of chemicalreactants matches the ratio of the constituent components in the finalgarnet electrolyte film assuming no mass loss. These precursors aremixed and milled. After about 8 hours, a plasticizer is added in anamount of approximately 3 weight % of the combined components. Solventis added in an amount of approximately 5-50 weight % of the combinedcomponents. Mixing and milling may optionally continue after theaddition of the plasticizer and solvent for another 12 hours. After thecompletion of the mixing and milling, the resulting slurry is filteredto remove any remaining grinding media and agglomerates or to ensure thehomogeneity of the particle sizes therein. The slurry can then be cast,e.g., by doctor blading, to prepare a thin film of unsintered greenfilm.

In some embodiments, the unsintered green film is then placed on top ofa Li-stuffed garnet setter plate to fabricate a Li-stuffed garnet solidelectrolyte. In such embodiments, the unsintered green film is sinteredon top of the Li-stuffed garnet setter plate to form a sintered garnetfilm. A metal foil or metal powder can optionally be placed between thesetter plate and the unsintered green film prior to sintering. The metalfoil or metal powder can be selected from the group consisting of: Ni,Cu, Fe, Al, Ag, alloys thereof, or combinations thereof. Additionalembodiments are described in further detail below.

In some examples, a setter plate is placed on top of the unsinteredgreen film which is itself on top of a Li-stuffed garnet setter plateand subsequently sintered to fabricate a Li-stuffed garnet solidelectrolyte.

In some examples, set forth herein is a method of using a Li-stuffedgarnet setter plate to fabricate a Li-stuffed garnet solid electrolytefor a rechargeable battery, wherein the method includes: placing a greenfilm of unsintered Li-stuffed garnet precursor materials between twoLi-stuffed garnet setter plates, and sintering the green film betweenthe two Li-stuffed garnet setter plates.

In some examples, set forth herein is a method of using a Li-stuffedgarnet setter plate to fabricate a Li-stuffed garnet solid electrolytefor a rechargeable battery, wherein the method includes placing a greenfilm of unsintered Li-stuffed garnet precursor materials on top of aLi-stuffed garnet setter plate; and sintering the green film on top ofthe Li-stuffed garnet setter plate to form a sintered garnet film.

In some examples, the methods herein further include placing a metalfoil or metal powder between at least one setter plate and the greenfilm prior to the sintering the green film. In some examples, themethods herein further include placing a metal foil or metal powderbetween the setter plate and the green film prior to the sintering thegreen film.

In some examples, the metal is Ni, Cu, Fe, Al, Ag, combinations thereof,or alloys thereof.

In some examples, the green film has a surface defined by a firstlateral dimension from 1 cm to 50 cm and a second lateral dimension from1 cm to 50 cm. In other examples, the green film has a surface definedby a first lateral dimension from 1 cm to 30 cm and a second lateraldimension from 1 cm to 30 cm.

In some examples, the green film has a thickness between 1 μm to about100 μm. In other examples, the green film has a thickness between 20 μmto about 100 μm.

In some examples, the sintering includes heating the green electrolytefilm and the two Li-stuffed garnet setter plates to between 450° C. and1300° C.

In some examples, the sintering comprises beating the green electrolytefilm and a Li-stuffed garnet setter plate to between 450 and 1300° C.

In some examples, the sintering comprises exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to anArgon:H₂ mixed atmosphere.

In some examples, the sintering comprises exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to an Argonatmosphere.

In some examples, the green film is an unsintered green film. In certainexamples, the green film is a tape-cast green film.

In some examples, the sintering comprises exposing, during the heating,the tape-cast green film and the two Li-stuffed garnet setter plates toan Argon:H₂:H₂O mixed atmosphere.

In some examples, the sintering comprises exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to anoxygen-containing atmosphere.

In some examples, the sintering comprises exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to9.5::Argon:H₂ atmosphere.

In some examples, the sintering produces a sintered Li-stuffed garnetsolid electrolyte less than 100 microns thick and more than 1 nm thick.In some examples, the sintering produces a sintered Li-stuffed garnetsolid electrolyte less than 80 microns thick. In some examples, thesintering produces a sintered Li-stuffed garnet solid electrolyte lessthan 70 microns thick. In certain examples, the sintering produces asintered Li-stuffed garnet solid electrolyte less than 60 microns thick.In certain examples, the sintering produces a sintered Li-stuffed garnetsolid electrolyte less than 50 microns thick. In certain examples, thesintering produces a sintered Li-stuffed garnet solid electrolyte lessthan 40 microns thick. In certain examples, the sintering produces asintered Li-stuffed garnet solid electrolyte less than 30 microns thick.In certain examples, the sintering produces a sintered Li-stuffed garnetsolid electrolyte less than 20 microns thick.

In some examples, the sintered Li-stuffed garnet solid electrolyteprepared by the methods herein has an ASR from between 0.5 Ω·cm² to 10Ω·cm² at 50° C. In other examples, the sintered Li-stuffed garnet solidelectrolyte has an ASR from less than 10 Ω·cm² at 50° C. In yet otherexamples, the sintered Li-stuffed garnet solid electrolyte has an ASRfrom less than 10 Ω·cm² at 0° C. In other examples, the sinteredLi-stuffed garnet solid electrolyte has an ASR from less than 20 Ω·cm²at −30° C. In still other examples, the sintered Li-stuffed garnet solidelectrolyte has an ASR from less than 20 Ω·cm² at −30° C. but more than1 Ω·cm². In some examples, the sintered Li-stuffed garnet solidelectrolyte has a thickness of 80μm and has an ASR from less than Ω·cm²at 50° C. In still other examples, the sintered Li-stuffed garnet solidelectrolyte has a thickness of 80 μm and has an ASR from less than Ω·cm²at 20° C.

In some examples, the sintered Li-stuffed garnet solid electrolyte has asurface roughness of from 0.1 μm Ra to 4 μm Ra, wherein Ra is anarithmetic average of absolute values of sampled surface roughnessamplitudes. In some other examples, the sintered Li-stuffed garnet solidelectrolyte has a surface roughness from 1.6 μm Ra to 2.2 μm Ra, whereinRa is an arithmetic average of absolute values of sampled surfaceroughness amplitudes. In some other examples, the sintered Li-stuffedgarnet solid electrolyte has a surface roughness 3.2 μm Ra to 3.7 μm Ra,wherein Ra is an arithmetic average of absolute values of sampledsurface roughness amplitudes.

In some examples, the methods include seasoning the two Li-stuffedgarnet setter plates by using each at least once in a sintering cycleprior to the step of placing a tape-cast film of unsintered Li-stuffedgarnet precursor materials between two Li-stuffed garnet setter plates.

In some examples, the methods include seasoning the two Li-stuffedgarnet setter plates by using each at least once In a heating andcooling (thermal) cycle prior to the step of placing a tape-cast film ofunsintered Li-stuffed garnet precursor materials between two Li-stuffedgarnet setter plates.

In some examples, the methods include using the two Li-stuffed garnetsetter plates at least once in a seasoning sintering cycle, wherein theusing is associated with a grain size increase in each of the twoLi-stuffed garnet setter plates, prior to the step of placing atape-cast film of unsintered Li-stuffed garnet precursor materialsbetween two Li-stuffed garnet setter plates.

In some examples, the methods include using the two Li-stuffed garnetsetter plates at least once in a seasoning sintering cycle for enlarginga grain size in each of the two Li-stuffed garnet setter plates.

In some examples, the methods include using the two Li-stuffed garnetsetter plates at least three time in a seasoning sintering cycle foreither, or both, enlarging a grain size in each of the two Li-stuffedgarnet setter plates or for reducing the tendency of the Li-stuffedgarnet setter plates to adhere to a film during a subsequent sinteringstep, wherein the seasoning is prior to the step of placing a tape-castfilm of unsintered Li-stuffed garnet precursor materials between twoLi-stuffed garnet setter plates.

In some examples, the methods comprising using the two Li-stuffed garnetsetter plates at least five time in a seasoning sintering cycle.

In some examples, the methods include depleting the Li concentration inthe garnet setter by using the two Li-stuffed garnet setter plates atleast one time in a seasoning thermal cycle. In some of these methods,the garnet setters have a reduced tendency to stick or adhere tosintering thin films.

In some examples, set forth herein is a method of using a Li-stuffedgarnet setter plate to fabricate a Li-stuffed garnet solid electrolytefor a rechargeable battery, wherein the method includes placing a greenfilm of unsintered Li-stuffed garnet precursor materials between twosetter plates selected from Li₂ZrO₃, xLi₂O-(1-x)SiO₂ (wherex=0.01-0.99), aLi₂O-bB₂O₃-cSiO₂(where a+b+c=1), LiLaO₂, LiAlO₂, Li₂O,Li₃PO₄, a Li-stuffed garnet, or combinations thereof, and sintering thegreen film between the two setter plates.

In some examples, set forth herein is a method of using a Li-stuffedgarnet setter plate to fabricate a Li-stuffed garnet solid electrolytefor a rechargeable battery, wherein the method includes placing a greenfilm of unsintered Li-stuffed garnet precursor materials between twosetter plates/selected from L₁₂ZrO₃, xLi₂O-(1-x)SiO₂ (wherex=0.01-0.09), aLi₂O-bB₂O₃-cSiO₂ (where a+b+c=1), LiLaO₂, LiAlO₂,_(Li2O), Li₃PO4, a Li-stuffed garnet, or combinations thereof; andsintering the green film between the two setter plates.

In any of the methods herein, the green film may be a tape-cast film.

In some examples, the sintering atmosphere comprises, Air, Argon,Nitrogen, an Argon:H₂ mixture, or an Argon:H₂:H₂O mixture.

In some examples, the binder is an acrylic binder.

In some examples, the binder poly methyl methacrylate or ethyl-methylmethacrylate.

In some examples, set forth herein is a method of sintering a green filmincluding a Li-stuffed garnet or the chemical precursors to a Li-stuffedgarnet, wherein the methods includes providing a green film including aLi-stuffed garnet or the chemical precursors to a Li-stuffed garnet; andsintering the green film in proximity to a Li-stuffed garnet setter suchthat the setter prevents the loss of Li from the sintering green film.

In some examples, set forth herein is a method of sintering a green filmincluding a Li-stuffed garnet or the chemical precursors to a Li-stuffedgarnet, wherein the method includes providing a green film comprising aLi-stuffed garnet or the chemical precursors to a Li-stuffed garnet; andsintering the green film in proximity to a Li-stuffed garnet setter suchthat the setter maintains the amount of Li in the sintering green film.

In some examples, set forth herein is a method of sintering a green filmincluding a Li-stuffed garnet or the chemical precursors to a Li-stuffedgarnet, including providing a green film comprising a Li-stuffed garnetor the chemical precursors to a Li-stuffed garnet; and sintering thegreen film in proximity to a Li-stuffed garnet setter such that thesetter maintains the amount of Li in the sintering green film, whereinthe sintering is in an over or furnace wherein the partial pressure ofLi(g) LiO(g), and/or L₁₂O(g) is between 10 and 10⁻⁵ Pascals (Pa).

In some of these methods, the green film is on top of at least oneLi-stuffed garnet setter.

In some examples, the methods herein, include placing a metal foil ormetal powder between the setter plate and the green film prior to thesintering the green film. In some examples, the metal is Ni, Cu, Fe, Al,Ag, combinations thereof or alloys thereof.

In some examples, the green film has a surface defined by a firstlateral dimension from 1 cm to 50 cm and a second lateral dimension from1 cm to 50 cm. In some examples, the green film has a thickness between1 μm to about 100 μm. In some examples, the green film has a thicknessbetween 10 μm to about 50 μm.

In some of the examples herein, the sintering comprises heating thegreen electrolyte film and the setter plate to between 450° C. and 1300°C.

In some examples, the sintering comprises exposing, during the heating,the green film and the two Li-stuffed garnet setter plate to an Argon:H₂mixed atmosphere.

In some examples, the sintering comprises exposing, during the heating,the green film and the Li-stuffed garnet setter plate to an Argonatmosphere.

In some examples, the green film is an unsintered green film. In some ofthese examples, the green film is a tape-cast green film.

In some examples, the sintering includes exposing, during the heating,the, tape-cast green film and the two Li-stuffed garnet setter plates toan Argon:H₂:H₂ O mixed atmosphere.

In some examples, the sintering includes exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to anoxygen-containing atmosphere.

In some examples, the sintering includes exposing, during the heating,the green film and the two Li-stuffed garnet setter plates to95:5::Argon:H₂ atmosphere.

In some examples, the sintering produces a sintered Li-stuffed garnetsolid electrolyte less than 100 microns thick and more than 1 nm thick.In some other examples, the sintering produces a sintered Li-stuffedgarnet solid electrolyte less than 50 microns thick. In some examples,the sintering produces a sintered Li-stuffed garnet solid electrolyteless than 40 microns thick. In some other examples, the sinteringproduces a sintered Li-stuffed garnet solid electrolyte less than 30microns thick. In some examples, the sintering produces a sinteredLi-stuffed garnet solid electrolyte less than 20 microns thick. In otherexamples, the sintered Li-stuffed garnet solid electrolyte has an ASRfrom between 0.1 Ω·cm² to 10 Ω·cm² at 0° C.

In some examples, set forth herein, during the sintering, the partialpressure of Li(g), LiO(g), or Li₂O(g) and is 10⁻¹ Pa. In other examples,the partial pressure of Li(g), LiO(g), or Li₂O(g) is 10⁻² Pa. In someother examples, the partial pressure of Li(g), LiO(g), or Li₂O(g) is10⁻³ Pa. In yet other examples, the partial pressure of Li(g), LiO(g),or Li₂O(g) is 10⁻⁴ Pa. In some other examples, the partial pressure ofLi(g), LiO(g), or Li₂O(g) is 10⁻⁵ Pa.

Polishing and Phase Assemblage

An example Li-stuffed garnet setter plate produced from method 200 isshown in FIG. 3A, which is a cross-sectional scanning electronmicrograph of a Li-stuffed garnet setter plate of the presentdisclosure. The image of FIG. 3A includes a scale marker and was takenin a scanning electron microscope (SEM) at an accelerating voltage of 10keV for a magnification of approximately 50×. The scale fear in FIG. 3Ais 1.0 mm. As is shown, the grain size of the Li-stuffed garnet setterplate in FIG. 3A is approximately 3 microns to approximately 5 microns.In other embodiments, the grain size of the Li-stuffed garnet setterplate is between 2 microns and 10 microns. The thickness of theLi-stuffed garnet setter plate is approximately 1.2 mm. In oneembodiment, Li-stuffed garnet setter plates having a thickness ofapproximately 1 mm to approximately 2 mm, a grain size of from 5 micronsto 10 microns, and cast. The plates may be cast into or later singulatedinto a square or rectangular format of the desired dimensions, forexample approximately 1.0 cm per side. Li-stuffed garnet setter platesthat are thinner than approximately 0.1 or 0.5 mm and/or have grains ofa d₅₀ larger than approximately 500 microns are prone to mechanicalfailure during use. The weight of the Li-stuffed garnet setter plateitself when combined with grains having a characteristic dimension(e.g., a diameter or length of a crystal edge) that is about thethickness of the setter plate, may cause formation and/or propagation ofinter-grain cracks. These cracks may cause the Li-stuffed garnet setterplates to fracture, rending them inadequate for continued use as setterplates.

Furthermore, the preferred grain size and surface features can beproduced by cycling a Li-stuffed garnet setter plate from two to fivetimes under temperatures used to produce Li-stuffed garnet solidelectrolyte (i.e., seasoning the setter plate). Furthermore, thepreferred grain size and surface features is produced when a Li-stuffedgarnet setter plate is placed in contact with Li-stuffed garnet solidelectrolyte and cycled according to the temperatures and pressuresdescribed in U.S. Patent Application Publication No. U.S. 2015/0099190,which published Apr. 9, 2015. This “sacrificial sintering” or “seasoningsintering” has the added benefit of preserving the lithium content andgarnet phase in both the setter plate and solid electrolyte. In betweenthe seasoning thermal cycles, the setter plates may be polished or notpolished.

The lithium stuffed garnets described herein include crystalline garnetin combination with amorphous garnet. The crystalline component of thesetter is the grains, which may be single crystals or which may bepolycrystalline agglomerates. In some examples, the grains of the garnetsetter are single crystals of garnet. In other examples, the grains ofthe garnet setter are polycrystalline. In the methods disclosed herein,seasoning the setters through thermal cycling has the unexpected benefitof conditioning the setter's such that the setters are prevented fromsticking to the sintering film that is placed between setter platesduring a sintering procedure.

FIG. 3B shows a Li-stuffed garnet setter plate that has been used in thepreparation of Li-stuffed garnet solid electrolyte, and thereforethermally cycled repeatedly (in this case from between about 10 timesand about 20 times) during the electrolyte sintering stage. As is shown,the setter plate itself is approximately 400 microns (0.4 mm) thick, andthe grains therein range from approximately 100 microns to approximately300 microns. This grain size has been found to grown in association withthe thermal cycling, which results in setters that stick less to a givensintering film. One benefit of seasoning the setter plates is to reducethe ability of the setter plate to absorb Li from a sintering Lielectrolyte.

Other benefits include a more crystalline garnet setter plate. Otherbenefits include a garnet setter plate lacking surface impurities. Otherbenefits include a garnet setter plate that has a lower chemicalpotential to absorb Li from the sintering garnet film. Additionally,thermally cycling the setter before first use with films reduces thetendency for sticking between setter and film. In some examples settersshould he thermally cycled from 1-5 times in addition to the primarysintering step.

In some examples, the setter plates are polished prior to each instanceof thermal cycling to expose a fresh surface. Without thermal treatmentthe first few uses of a setter can result in increased prevalence ofsticking between setter and thin film.

FIG. 4 illustrates surface roughness measurements of four exampleLi-stuffed setter plate produced by the method 200. The top two imagesare for polished setter plates, and the bottom two images are forunpolished setter plates. As can be seen, even prior to polishing, eachof the rectangular sample areas of a setter plate (from approximately1.4 mm to 2 mm per side) has a surface topography that Is quite uniform.As can be seen, occasional protrusions of up to 50 microns extend fromportions of the surface. This produces a surface roughness forLi-stuffed garnet setter plates having small grains (2 microns to 10microns) from approximately 1.8 Ra to approximately 2.4 Ra when polishedcompared to from approximately 2.0 Ra to 2.7 Ra when left unpolished.For Li-stuffed garnet setter plates having large grains (100 microns to400 microns), the surface roughness is front 3.5 Ra to 5.0 Ra wheneither polished or unpolished. Ra is a unit for quantifying surfaceroughness, and is calculated from an arithmetic average of all absolutevalues of roughness amplitudes measured on a given sample.

In some other examples, another way to describe the Li-stuffed garnet,setter plates described herein includes the R_(t) parameter which isequal to R_(peak)−R_(valley) and represents the maximum peak height in agiven surface roughness measurement. In some examples, the R_(t) canrange from about 1 μm to 30 μm. In some examples, the R_(t) can rangefrom about 1 μm to 28 μm. In some examples, the R_(t) can range fromabout 10 μm to 30 μm. In some examples, the R_(t) can range from about15 μm to 30 μm.

The uniform topography with only small protrusions (generally removed orreduced in height during polishing) is one of the unexpected benefits ofLi-stuffed setter plate This uniform topography facilitates a uniformand planar surface on Li-stuffed solid electrolytes produced using theLi-stuffed setter plates, which in turn encourages intimate electricalcontact between the solid electrolyte and corresponding positive andnegative electrodes of a battery cell.

The effect of re-polishing (i.e., polishing between thermal cycling)Li-stuffed garnet setter plates prior to their use in sintering anunsintered film, and grain size of Li-stuffed garnet setter plates onthe phase produced in Li-stuffed garnet solid electrolyte has also beenstudied. FIGS. 5A-5D illustrate X-ray diffraction patterns (produced byCu K-alpha, and measured via a 2-theta detector configuration) ofLi-stuffed garnet solid electrolyte produced by various combinations ofpolished and unpolished Li-stuffed garnet setter plates of varying grainsizes. In the graph of FIG. 5A, an X-ray diffraction pattern is shown ofa Li-stuffed solid electrolyte produced using a re-polished Li-stuffedgarnet setter plate having small grains of a d₅₀ of approximately 2-10um. In the graph of FIG. 5B, an X-ray diffraction pattern is shown of aLi-stuffed solid electrolyte produced using an unpolished Li-stuffedgarnet setter plate having small grains of a d₅₀ of approximately 2-10um. In the graph of FIG. 5C, an X-ray diffraction pattern is shown of aLi-stuffed solid electrolyte produced using a re-polished Li-stuffedgarnet setter plate having large grains of a of approximately 100-400um. In the graph of FIG. 5D, an X-ray diffraction pattern is shown of aLi-stuffed solid electrolyte produced using an unpolished (i.e., notrefinished after thermally cycling the setter after it was initiallyproduced and then polished prior to the thermal cycling) using aLi-stuffed garnet setter plate having large grains of a d₅₀ ofapproximately100-400 um. As is evident upon inspection, all of the X-raydiffraction patterns show the presence and retention of the Li-stuffedgarnet phase in the sintered film.

Highly conductive garnet electrolyte were prepared using Li-stuffedgarnet setter plates that are polished and have grain sizes fromapproximately 100 microns to approximately 400 microns. Other highlyconductive garnet electrolytes were prepared using unpolished Li-stuffedgarnet setter plates having grain sizes from approximately 100 micronsto approximately 400 microns. Some other highly conductive garnetelectrolyte were prepared using Li-stuffed garnet setter plates arethose that are unpolished and have a grain size from approximately 2microns to 10 microns. Equally conductive garnet electrolyte wereprepared using Li-stuffed garnet setter plates are those that arepolished and have a grain size from approximately 2 microns to 10microns.

Method of Using Setters

FIG. 6 illustrates a method 600 of using Li-stuffed garnet setter platesto fabricate Li-stuffed garnet solid electrolyte, in an embodiment. Atape-cast “green film” (i.e., a film of unsintered Li-stuffed garnetprecursor materials, binders, and other materials used in thepreparation of Li-stuffed garnet solid electrolyte as described in U.S.Parent Application Publication No. U.S. 2015/0099190, which, publishedApr. 9, 2015, which is incorporated by reference herein), and isreceived 604 in preparation for sintering. The tape-cast green film isplaced between two Li-stuffed garnet setter plates of the presentdisclosure in step 608. In some examples, a tape-cast green film isplaced on top of a Li-stuffed garnet setter plate. In one embodiment,each of Li-stuffed garnet setter plates is approximately square in shapefrom a plane view with approximately 10 cm on each of four sides, and isapproximately 1 mm to approximately 2 mm thick. Thus placed, the solidelectrolyte “green film” is sintered 612 in a 99.94:0.06::Argon:H₂atmosphere at about 1100° C., although temperatures from approximately850° C. to approximately 1300° C. have also been found to be effectiveat producing Li-stuffed garnet phase in the sintered electrolyte. Insome examples, the green film is sintered in an Argon:H₂ atmosphere at850° C. In some examples, the green film is sintered in an Argon:H₂atmosphere at 900° C. In some examples, the green film is sintered in anArgon:H₂ atmosphere at 950° C. In some examples, the green film issintered in an Argon:H₂ atmosphere at 1000° C. In some examples, thegreen film is sintered in an atmosphere at 1050° C. In some examples,the green film is sintered in an Argon:H₂ atmosphere at 1100° C.Sintering is performed from 0.5 hours to 6 hours. In some examples,sintering is performed until the green film achieves its maximumpossible density. In other examples, the solid electrolyte “green film”is sintered 612 in a 95.5::Argon:H₂ atmosphere at about 1100° C.,although temperatures from approximately to approximately 1300° C. havealso been found to be effective at producing Li-stuffed garnet phase inthe sintered electrolyte. Sintering is then performed from 0.5 hours to6 hours (e.g., 4 hours).

For example, sintering can be performed for about 0.5 hours, 1 hour, 2hours, 3 hours, 4 hours, 5 hours, 6 hours, or for any duration of timebetween any two of these values.

In some examples, the green film is sintered in a Nitrogen:H₂ atmosphereat 850° C. In some examples, the green film is sintered in a Nitrogen:H₂atmosphere at 900° C. In some examples, the green film is sintered in aNitrogen:H₂ atmosphere at 950° C. In some examples, the green film issintered in a Nitrogen:H₂ atmosphere at 1000° C. In some examples, thegreen film is sintered in a Nitrogen:H₂ atmosphere at 1050° C. In someexamples, the green film is sintered in a Nitrogen:H₂ atmosphere at1100° C.

In some examples, the green film is sintered in a Nitrogen atmosphere at850° C. In some examples, the green film is sintered in a Nitrogenatmosphere at 900° C. In some examples, the green film is sintered in aNitrogen atmosphere at 950° C. In some examples, the green film issintered in a Nitrogen atmosphere at 1000° C. In some examples, thegreen film is sintered in a Nitrogen atmosphere at 1050° C. In someexamples, the green film is sintered in a Nitrogen atmosphere at 1100°C.

In some examples, an oven is heated from room temperature to thesintering temperature with the setter plates and the unsintered filmtherebetween inside the heating oven. In some other examples, thesamples are placed into an oven that is already hot. In some examples,the samples are cooled naturally by removing them from the oven. Forexample, the samples can be removed from the oven and placed at roomtemperature (about 22° C. to 25° C.) In other examples, the samples arecooled by slowly reducing the temperature of the oven. Cooling protocolsare used so as to avoid thermal shock of the ceramic.

The setter plates and solid electrolyte are removed 616 from thefurnace. One unexpected benefit of Li-stuffed garnet setter plates ofthe present disclosure (in addition to preserving the Li-stuffed garnetphase of the solid electrolyte mentioned above) is the low adhesion ofLi-stuffed garnet setter plates to the solid electrolyte and therelatively beneficial density of the Li-stuffed garnet setter platescornered to commercially available setter plates conventionally usedsuch as porous Yttria stabilized Zirconia, alumina, graphite. Because ofthe appropriate density and low adhesion, the Li-stuffed garnet setterplates are removed from the Li-stuffed garnet solid electrolyte withoutdamaging the solid electrolyte, which can be relatively fragile whenonly from approximately 10 microns to approximately 100 microns thick.This range of thickness values of the solid electrolyte is useful forproducing a solid slate battery having adequate ionic conductivity andenergy delivery rates, as mentioned above. Commercially available setterplates (such as alumina, zirconia, and platinum) are generally notsuitable for use (e.g., reactive) in the production, of Li-stuffedgarnet solid electrolyte because they stick to or adhere to the sinteredfilm and will often cause cracking or mechanical failure, and poorelectrical properties, of the solid electrolyte having a thickness from10 microns to 100 microns.

Electrical Performance

While the benefits to the mechanical performance of setter plates havebeen presented above for Li-stuffed garnet setter plates of the presentdisclosure, benefits are also present with respect to electricalperformance, specifically the ionic conductivity, of Li-stuffed garnetsolid electrolyte produced using Li-stuffed garnet setter plates of thepresent disclosure.

Lithium-stuffed garnet films were fabricated according to the method inFIG. 6. The films were characterized by an empirical formulaLi₇La₃Zr₂O₁₂Al₂O₃. The films were sintered between lithium-stuffedgarnet setter plates at 1150° C. for 6 hours. After sintering, the filmswere approximately 50 μm thick and circularly shaped with a top surfacearea of approximately 0.5 cm². Area specific resistance or “ASR,” asdescribed in U.S. Patent Application Publication No. U.S. 2015/0099190,which published Apr. 9, 2015, was measured by electrical impedancespectroscopy for these films at 20° C., 50° C, 60° C., or 80° C. Both ACand DC impedance test were conducted on these films with lithiumelectrodes deposited on each side. The results are tabulated below inTable 1, wherein R1 represents the bulk resistance, R2 represents theinterfacial resistance, and ASR equals (R2/2)*Area, where the factor of2 is to account for the 2 interfaces in the test. In this Example, thearea was approximately 0.5 cm².

TABLE 1 R1 (Ω) R1 (Ω) ASR (Ωcm²) 80° C.  9.9 ± 0.1 0.0 0 60° C.   16 ±0.1 0.0 0 50° C. 20.9 ± 0.2 0.0 0 20° C. 46.2 ± 0.4 6.5 1.6

FIG. 7 shows an Arrhenius plot of EIS (AC Impedance) test results at 80°C, 60° C., 50° C. and 20° C. on three Li-stuffed garner solidelectrolyte samples in a symmetric Li|Garnet|Li cell. A conductivityvalue 1.03E-3 S/cm at 60° C. was observed. These results showsurprisingly high ionic, conductivity for Li-stuffed garnet solidelectrolytes prepared using the garnet setter plates of the Instantdisclosure. As indicated by FIG. 7, low interfacial impedance values areachievable when metallic lithium is deposited on the Li-stuffed garnetelectrolyte after fabrication is completed according to the method 600.FIG. 7 is an Arrhenius plot of conductivity as function of 1000/T forthe films tested.

FIG. 8 shows a lithium plating and stripping experiment. In thisExample, Lithium-stuffed garnet films were fabricated according to themethod in FIG. 6. The films were characterized by an empirical formulaLi₇La₃Zr₂O₁₂Al₂O₃. The films were sintered between lithium-stuffedgarnet setter plates at 1150° C. for 6 hours. After sintering, the filmswere approximately 50 μm thick, and circularly shaped with a top surfacearea of approximately 0.5 cm². These films were tested by conducting aninitial plating step of Li at 0.1 mA/cm² (for 5 minutes), followed by aplating step of Li at 0.2 mA/cm² (for 5 minutes) and then followed by aplating step of Li, at 0.4 mA/cm² (for 15 minutes), followed byopen-circuit voltage (OCV) steps for 2 minutes. This was followed bycycling step of 10 cycles of 0.2 mA/cm² for 120 s in each polarity,interspersed with an OCV step of 30 s. A Final step including a fullstrip of Li at 0.4 mA/cm² was then performed. The data in FIG. 8 wasobserved in a DC Test of a symmetric Li|Garnet|Li cell.

In another Example, lithium-stuffed garnet films were fabricatedaccording to the method in FIG. 6. The films were characterized by ahempirical formula Li₇La₃Zr₂O₁₂.Al₂O₃. The films were sintered betweenlithium-stuffed garnet setter plates at 1150° C. for 6 hours. Aftersintering, the films were approximately 50 μm thick and circularlyshaped with a top surface area of approximately 0.5 cm². These filmswere tested as shown in FIG. 9, which shows an example EIS plot of theat 60° C. This plot demonstrates an ASR (area specific resistance)=(DCImpedance−AC Bulk Impedance)/2*Area=(22 Ω−14.8 Ω)/2*0.5 cm²=1.8 Ω·cm².These results, show surprisingly low impedance for Li-stuffed garnetsolid electrolytes prepared using the garnet setter plates of theinstant disclosure.

Setter Performance

A series of green films were prepared as follows including garnetprecursors to Li₇Li₃Zr₂O₁₂Al₂O₃ and were sintered between either ZrO₂setter plates, Al₂O₃ setter plates or lithium stuffed garnet setterplates characterized by the composition Li₇Li₃Zr₂O₁₂Al₂O₃. As shown inFIG. 10 (top, part A), the film sintered between ZrO₂ setter plates didnot retain the garnet crystal structure and evidenced a complete loss ofthis garnet phase. As shown in FIG. 10 (middle, part B), the filmsintered between Al₁O₃ setter plates also did not retain the garnetcrystal structure though some XRD reflections associated with garnet areobserved. FIG. 10, part B, also shows that some amorphous material waspresent post-sintering. However, as shown in FIG. 10 (bottom, part C),the film sintered between lithium stuffed garnet setter platescharacterized by the composition Li₇Li₃Zr₂O₁₂Al₂O₃ did retain the garnetcrystal structure. The results in parts A and B of FIG. 10 may he due tothe loss of Li from the sintering green film on account of thedifference In chemical potential for the Li in the sintering green filmas compared to in either the ZrO₂ setter or in the Al₂O₃ setter.

Setter Conditions

As described in Ikeda, Y., et al., Journal of Nuclear Materials 97(1981) 47-58 and also Kato, Y, et al. Journal of Nuclear Materials 203(1993) 27-35, various lithium containing oxides have a measureable Livapor pressure. When heated, lithium compounds such as L₂ZrO₃ and canvolatilize and introduce gaseous species, such as but not limited toLi(g), LiO(g), Li₂O(g) and O₂(g). Other material, such as Li₅AlO₄ orLiAlO₂, LiAl₅O₈ can also volatile these species. The present disclosurerinds that by using Li-stuffed garnet setter plates, the partialpressure of these species, such as Li, LiO(g), or Li₂O(g) can bemaintained between 1 to 10⁻⁵ Pascal (Pa) range. In some examples, thepartial pressure of the volatile Li species is 1 Pa. In some examples,the partial pressure of the volatile Li species is 10⁻¹ Pa. In someexamples, the partial pressure of the volatile Li species is 10⁻² Pa. Insome examples, the partial pressure of the volatile Li species is 10⁻³Pa. In some examples, the partial pressure of the volatile Li species is10⁻⁴ Pa. In some examples, the partial pressure of the volatile Lispecies is 10⁻⁵ Pa. This range has been found to be useful formaintaining the Li content in a sintering green film. In some examples,the setter plates used herein maintain, within a sintering over orfurnace, a partial pressure of volatile Li between.

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to heexhaustive or to limit the claims to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible In light of the abovedisclosure.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the disclosure be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of theinvention, which is set forth in the following claims.

1. A setter plate for fabricating solid electrolytes of a rechargeablebattery, the setter plate comprising: a Li-stuffed garnet compoundcharacterized by the formula Li_(x)La_(y)Zr_(z)O_(t).qAl₂O₃, wherein4<x<10, 1<y<4, 1<z<3, 6<t<14, 0≦q≦1; a surface defined by a firstlateral dimension from 2 cm to 30 cm and a second lateral dimension from2 cm to 30 cm; and a thickness from 0.1 mm to 100 mm. 2.-3. (canceled)4. The setter plate of claim 1, wherein the thickness is from 0.1 mm to10 mm. 5.-9. (canceled)
 10. The setter plate of claim 1, wherein thesurface has a surface roughness from 1.0 μm Ra to 4 μm Ra, wherein Ra isan arithmetic average of absolute values of sampled surface roughnessamplitudes. 11.-116. (canceled)
 117. The setter plate of claim 1 havinga flatness of between 0.1 μm and 100 μm.
 118. The setter plate of claim1 having a flatness of between 0.5 μm and 20 μm.